Structure Determination from S/TEM Images and Theoretical Analysis of Complex Nanoscale Materials

The knowledge of atomistic structure of complex nanomaterials is needed to fully leverage the theoretical capabilities to gain insights into the atomic scale phenomena. However, often it is challenging to determine the underlying 3D atomistic structure corresponding to a S/TEM image due to one-to-many problem. We developed Ingrained software package [1], which can construct the atomistic structure of grain boundary interfaces from S/TEM images using only the observable experimental parameters as inputs. We apply the Ingrained package to determine the structures of domain boundaries, from STEM images, and analyze the oxygen instability during charge-discharge cycles [2].<br/> <br/>Complex interfacial structures with local disorder result in low resolution regions in the S/TEM images. To determine atomistic structure of such regions, we further integrate local structure optimization routine using DFT calculations with the Ingrained package and developed a multi-objective evolutionary algorithm called FANTASTX (Fully Automated Nanoscale To Atomistic Structure from Theory and eXperiments). We apply FANTASTX to create models of the interface structure in Al-Si hetero-interfaces from STEM images to study the structural origin of two-level systems for quantum applications. Finally, denoised phase contrast TEM images of Pt nanoparticle on ceria substrate in CO gaseous environment are used to create experimentally observed Pt nanoparticle structures to study the atomistic phenomena behind the observed surface dynamics. Both Ingrained and FANTATSX software serve as computational tools to invert the experimental TEM images of interfaces, nanoparticles or 2D materials to create high-fidelity atomistic structures for further theoretical analysis.<br/> <br/>[1] E. Schwenker, V. S. C. Kolluru, et. al., Ingrained: An Automated Framework for Fusing Atomic-Scale Image Simulations into Experiments. <i>Small</i> 2022<br/>[2] X. Liu*, G-L. Xu*, V. S. C. Kolluru, et. al., Origin and regulation of oxygen redox instability in high-voltage battery cathodes<i>.</i> <i>Nature Energy</i> 2022